Tripod roller for a constant velocity universal joint

ABSTRACT

A tripod type constant velocity universal joint comprising an outer joint member having longitudinal recesses arranged in spaced relationship on a periphery thereof, and trunnions symmetrically arranged on a tripod spider, said trunnions located in said recesses of the outer joint member by tripod rollers mounted on rolling elements, characterized in that an inner ring formed without chip removal from sheet metal is arranged between each trunnion and respective rolling elements, the inner ring, the tripod roller and the rolling elements form a roller assembly, and the inner ring comprises at least first and second radially stepped end flanges which form radially inner stops for the rolling elements and radially outer stops for the tripod roller.

The invention concerns a constant velocity universal joint of a tripodtype comprising an outer joint member having longitudinal recessesarranged in space relationship on a periphery thereof and trunnionssymmetrically arranged on a tripod spider, said trunnions engaging intosaid recesses of the outer joint member by tripod rollers mounted on torolling elements.

In a universal joint of this type known from DE-A-41 13 944, the rollingelements are mounted directly on the trunnion of the inner joint member,that is to say, on the tripod spider. Stop rings guided on the trunnionat the ends of the rolling elements form an axial stop for the rollingelements while axial locking is achieved by a circlip against which thestop ring bears, the circlip being guided in a circumferential groove onthe free end of the trunnion. This structure necessitates a polished andsurface-hardened rolling element raceway on the trunnion. Assemblyinvolves several time-consuming and therefore costintensive work stepsfor the mounting of individual components. Thus, for example, the stoprings have to be pushed onto the trunnion, the circlip has to beinserted into the circumferential groove and be engaged by the profiledstop ring before the rolling elements can be inserted. Finally thetripod roller is pushed over the rolling elements.

OBJECTS OF THE INVENTION

It is an object of the invention to create a tripod type universal jointhaving fewer components and an optimized design space requirement sothat manufacturing and assembly costs of the constant velocity universaljoint are reduced.

THE INVENTION

A tripod type constant velocity universal joint comprising an outerjoint member having longitudinal recesses arranged in spacedrelationship on a periphery thereof, and trunnions symmetricaly arrangedon a tripod spider, said trunnions engaging into said recesses of theouter joint member by tripod rollers mounted on rolling elements, ischaracterized in that an inner ring (2) formed without chip removal fromsheet metal is arranged between each trunnion (15) and respectiverolling elements (3), the inner ring (2), the tripod roller (4) and therolling elements (3) form a roller assembly (1), and the inner ring (2)comprises stepped end flanges (5,6,10) which form separate, mutuallyoffset axial stops for the rolling elements (3) and the tripod roller(4). The solution of the invention comprises arranging an inner ring ofsheet metal between the rolling elements and the trunnion, with theinner ring forming a roller assembly with a tripod roller and therolling elements.

GB-B-15 74 765 discloses a rolling bearing having an inner ring whoseflanges bent at a right angle form a common axial stop for the rollingelements and the outer ring of the rolling bearing. This prior artstructure is not suitable for use in constant velocity universal jointsbecause in such joints provision must be made for a relative axialdisplacement between the rolling elements and the tripod roller. Thisrequirement is met by the inner ring of the invention which comprisesend flanges forming separate, mutually offset axial stops for therolling elements and the tripod roller.

The inner ring in the configuration of the invention comprises flangeswhich form axially offset stops thus advantageously permitting a freeorientation of the tripod roller within the constant velocity universaljoint. Particularly during operation of the joint at large bend angles,a relatively large axial displacement takes place between the rollingelements and the tripod roller. The tripod assembly of the inventionadvantageously comprises fewer components than known structures so thatcosts are reduced. Moreover, the tripod assembly of the invention isfurther characterized by a smaller overall axial length. Two thin-walledflanges of the inner ring of the invention replace the prior art stoprings as well as the circlip with its additional requirement of acircumferential groove. The reduced overall axial length effects areduction of the design space requirement of the constant velocityuniversal joint.

A further cost reduction results from the fact that the hithertorequired surface treatment, e. g. hardening and grinding of the trunnionto enable a direct guidance of the rolling elements thereupon can beomitted by use of the inner ring of the invention. The inner ring formedfrom thin sheet metal advantageously has no negative influence on theradial design dimensions of the constant velocity universal joint.

In an advantageous embodiment of the invention, the roller assembly is apre-assemblable unit consisting of the tripod roller, the rollingelements and the inner ring whose end flanges assure a coherence of theassembly. Advantageously, this pre-assembled unit can be mounteddirectly on the trunnion of the tripod spider so that mounting issimplified and time and cost factors are optimized. Moreover, theinseparable unit being safe from falling apart during mounting, it issuitable for mounting by automatic means such as robots. Anotheradvantage is the simplification of storage and stockkeeping of spareparts.

In a further embodiment of the invention the flanges have a radiallystepped configuration with the axial extent of the first step beingmatched to the length of the rolling elements. The second step on eachside of the tripod roller comprises an axial stop spaced from the end ofthe tripod roller so that a displacement of the tripod roller relativeto the rolling elements is possible in both directions. The axial stopfor the tripod roller may be optionally configured as a flange or as aretaining lug. The axial extents of the axial stops for the tripodroller can differ from each other. Due to differing displacements of thetripod roller in the two axial directions in the installed state, theflange nearer the free end of the trunnion is arranged at a larger axialdistance than the opposite flange.

The flange of the inner ring nearer the center of the tripod spidercomprises elastic retaining lugs which overlap the inner diameter of thetripod roller in radial direction and yield resiliently during assembly.This enables the tripod roller to be pushed in an axial direction on tothe inner ring already equipped with rolling elements, and the innerring to be inserted into the reception bore of the tripod roller.

The inner ring is secured to the trunnion by an interference fit, withthe inner ring being matched in dimension to the outer contour of thetrunnion. The inner ring may also be fixed by axial securing, preferablyby a local radial stamping of the end of the trunnion towards the rollerassembly.

The fatigue strength of the trunnion can be improved if an undercut isprovided in the region of transition between the peripheral surface ofthe trunnion and the inner portion of the tripod spider. The undercut ispreferably in the form of a circumferential groove which is an effectivemeans for reducing stress concentration and stress peaks in thetrunnion.

The inner ring of the invention is made by deep drawing which leads to afurther reduction of costs particularly in large-scale manufacturing.

To obtain the required high strength, the inner ring has be heattreated. Preferably, the entire inner ring would be subjected to theheat treatment, however, as an alternative, only one side of the innerring, i. e. the raceway of the rolling elements may be subjected to asurface treatment. The advantageously thin-walled inner ring can adaptitself to the contour of the peripheral surface of the trunnion despitesurface treatment.

The components forming the roller assembly, viz., the inner ring, therolling elements and the tripod roller are all size-matched. Thisassures that the required radial play in the constant velocity universaljoint is guaranteed after the installation of the tripod assembly.

Further features of the invention will become evident from the drawingsand the description of the figures which show one example of embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-section of a roller assembly of theinvention;

Fig. 2 shows the roller assembly of FIG. 1 in the installed state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a roller assembly 1 of the invention composed of an innerring 2, rolling elements 3 and a tripod roller 4. The axial extent ofthe inner ring 2 which is made as a deep drawn sheet metal part islarger than the axial extent of the tripod roller 4. Flanges 5, 6 of theinner ring 2 bear against ends of the rolling elements 3. At itsradially outer end, the flange 5 merges into an axial portion 7 on whoseouter periphery is arranged a plurality of spaced retaining lugs 8a and8b. The flange 6 comprises a similarly formed axial portion 9 which,however, instead of having lugs, merges into a flanges 10a and 10b.Starting from the neutral position shown in FIG. 1, the tripod roller 4can be axially displaced through a distance "X" before abutting againstthe flanges 10a and 10b. An axial displacement of the tripod roller 4 inthe opposite direction is stopped at the retaining lug 8a and 8b or thetripod spider 11 (see FIG. 2). The retaining lugs 8 arranged on theouter periphery of the axial portion 7 can be made, for example, bymaking local stampings or incisions in the portion 7 and bending theseradially outwards. For assembling the components of the tripod assembly1, these lugs 8a and 8b are elastically deformed. They also consitute asafety device against separation of the individual components from theroller assembly 1.

FIG. 2 shows the tripod roller assembly 1 as installed in a constantvelocity universal joint 12. The convex outer surface of the tripodroller 4 serves to guide the tripod roller assembly 1 in the outer ring16 which is inserted into a longitudinal recess 14 of the outer jointmember 13. The inner ring 2 is pressed onto the trunnion 15 of thetripod spider 11 whereby the inner contour of the inner ring 2 adaptsitself to the peripheral surface 17 of the trunnion 15. From FIG. 2 itcan be clearly seen that an unobstructed axial displacement of thetripod roller 4 is enabled by the inner ring 2 of the invention in casethe constant velocity universal joint 12 has to bridge large angles ofbend. An undercut 18 made in the form of a radial circumferential groovein the peripheral surface 1 7 of the trunnion 15 at the transition tothe tripod spider 11 serves to improve the strength of the trunnion 15.

List of Reference Numbers

1 Roller assembly

2 Inner ring

3 Rolling elements

4 Tripod roller

5 Flange

6 Flange

7 Portion

8 Retaining lug

9 Portion

10 Flange

11 Tripod spider

12 Constant velocity universal joint

13 Outer joint member

14 Recess

15 Trunnion

16 Outer ring

17 Peripheral surface

18 Undercut

We claim:
 1. A tripod type constant velocity universal joint comprisingan outer joint member having longitudinal recesses arranged in spacedrelationship on a periphery thereof, and trunnions symmetricallyarranged on a tripod spider, said trunnions located in said recesses ofthe outer joint member, rolling elements surrounding the trunnions andhaving tripod rollers mounted thereon, characterized in that an innerring (2) formed without chip removal from sheet metal is arrangedbetween each trunnion (15) and the respective rolling elements (3), theinner ring (2), the tripod roller (4) and the rolling elements (3) forma roller assembly (1), and the inner ring (2) comprises at least firstand second radially stepped end flanges (5, 6) extending so to radiallyoverlap the radially inner and outer surfaces of the rolling elementsand the tripod roller, each of the stepped flanges including radiallyinner stops (8a, 8b) for engaging the rolling elements (3) and radiallyouter stops (10a, 10b) for engaging the tripod roller (4).
 2. Auniversal joint of claim 1 wherein the tripod roller (4), the rollingelements (3) and the inner ring (2) constitute a pre-assemblable rollerassembly (1).
 3. A universal joint of claim 1 wherein the rollingelements (3) are supported directly on the radially inner stops (8a, 8b)of the flanges (5, 6), and the radially outer stops (10a, 10b) areaxially spaced from the radially inner stops (8a, 8b) by a first axialportion (9) and a second axial portion (7).
 4. A universal joint ofclaim 3 wherein an axial length of the first axial portion (9) is largerthan an axial length of the second axial portion
 7. 5. A universal jointof claim 1 wherein a plurality of retaining lugs (8) are arranged inspaced relationship on a periphery of the second axial portion (7).
 6. Auniversal joint of claim 1 wherein the inner ring (2) is pressed ontothe trunnion (15).
 7. A universal joint of claim 1 wherein an axialsecuring for the inner ring (2) is axially secured on an end of thetrunnion (15).
 8. A universal joint of claim 1 wherein a radialcircumferential undercut (18) is arranged in a transition region betweena peripheral surface (17) of the trunnion (15) and the tripod spider(11).
 9. A universal joint of claim 1 wherein the inner ring (2) is madeas a deep drawn part.
 10. A universal joint of claim 1 wherein at leasta part of the inner ring (2) is subjected to a heat treatment forobtaining a raceway for the rolling elements (3).
 11. A universal jointof claim 1 wherein all components of the roller assembly (1) areselected by matching sizes to respect a required radial play in theuniversal joint (12).